Method of recovering the constituents of scrap bi-metal



R. A. WILKlNS ETAL 2,403,419 METHOD OF RECOVERING THE CONSTITUENTS OFSCRAP BI-METAL July 2, 1946.

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METHOD OF RECOVERING THE CONSTITUENTS OF SCRAP BI-METAL 2 Sheets-Sheet 2Filed April 15, 1943 7 4 W W, a q fil 9% W m::: W E w Invenim ns:

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Patented July 2, 1946 LIETHOD F BECOVERING ENTS OF SCRAP BI-METALRichard A. Wilkins and Edward N. Y., assignors to Rever corporated, NewYork,

Maryland THE CON STITU- S. Bunn, Rome,

e Copper and Brass In- N. Y., a corporation of Application April 15,1943, Serial no. 483,142

Our invention relates to separately recovering cuprous and ferrousmaterials from scrap consisting of iron or steel and associated copperor brass, this application being a continuation-inpart of applicantsNumber 464,420, filed November 3, 1942.

A common form of such scrap ls sheet bi-metal consisting of sheet mildsteel coated with a welded on layer of copper or brass suchas gildingmetal, the latter consisting of a brass containing about 90% copper andzinc. A typical example of such scrap is sheet mild steel about 0.05 ofan inch thick, containing about 0.05 to 0.15 carbon, coated with a sheetof gilding metal about 0.01 of an inch thick welded over its entiresurface to Another form of such scrap consists from shells having coppershell bands,

the steel. of turnings such scrap steel, commonly containing about 0.8to 0.5% carbon, mixed .With copper turnings. Other common forms of scrapconsisting of mild or other low carbon steel mixed or otherwiseassociated with cuprous material are sheet steel or wire coated withcopper or brass other than gilding metal. In all these instances theferrous material forms the major portion of the scrap, commonly 70 to85% thereof, and the cuprous material whether in the form of copper orbrass the minor portion.

-It is highly desirable to recover the importantly strategic metalcopper at present tied up in scrap of the above nature, enormousquantities of which, particularly in the form of sheet mild steel coatedwith gilding metal, are now available. It has heretofore been proposedto effect this recovery by leaching the scrap with ammoniacal compounds,and, although this proposed process is feasible from a technicalstandpoint, its employment nevertheless is objectionable from aneconomic standpoint because of the high operating costs and high initialcapital investment involved and by reason of the plant designed forperforming the process on a commercial scale involving the use of largeamounts of strategic materials. It has also been proposed to eifect therecovery, in connection with sheet mild steel scrap coated with glidingmetal, by heat treating and chlorinating the scrap to render the cuprousmaterial brittle andremove it as a powder by tumbling or otherwisejarring the scrap so treated, but no practical way has been evolved ofpractising this method on a commercial scale. Further, it has beenproposed to take advantage of thelower melting "point of the cuprousmaterial, as compared to that of the ferrous material, by heatingpending application Serialthe scrap to a temperature less than that ofiron but above that of the cuprous material so as to melt the latteroff, but this it has been found is entirely impractical because of thinlayers of the consisting of turnings of low carbon molten cuprousmaterial strongly adhering to the ferrous material on account of thesurface tension phenomena involved.

According to the present invention, the ferrous and cuprous materials ofthe scrap may be separately recovered at a minimum of expense in respectto initial capital investment and operating.

costs. Further, the practice of the invention on a commercial scale doesnot involve the use of great amounts of strategic materials, form suchpractice there need be employed only existing equipment, or the samewith slight and inexpensive modifications, now available at mostmetallurgical and fabricating plants dealing with ferrous materials.

Applicants have found, that by properly melting and treating the scrap,the ferrous and cuprous constituents of the melt may be renderedsubstantially mutually insoluble when in a molten condition, and, thatby observing certain precautions, the molten mixture may be caused tostratify by reason of the diiferent densities of these constituents,thus permitting cuprous material to be tapped from the bottom portion ofthe melt and ferrous material to be separately tapped from theupperportion of the melt.

As an alternative procedure the stratified melt may be allowed tosolidify and the cuprous material may be separated mechanically from theferrous material. For example, the containers in which the metals arepermitted to stratify may be in the form of vertically positioned,elongated, highly heated, fire-clay molds, preferably portions of thebillets by a sawing operation, or,

in many instances, by breaking them apart at the line of demarcationbetween the two portions by striking the billet with a sledge or steamhammer.

In respect to making the ferrous and cuprous materials of the meltmutually insoluble, applicants have found that if the scrap is melted toproduce a molten mixture of copper and mild or other low carbon steelvery high percentages of taining 4.3% carbon,

the molten copper will dissolve into the molten steel, particularly whena high temperature of the melt is maintained in an attempt to promotestratification as hereinafter explained. In fact it has been found thatsubstantially pure iron will dissolve copper in substantially allproportions. On the other hand, applicants have found that if the steelis enriched with carbon the solubility of the copper therein ispronouncedly decreased. For example, if the steel is enriched withcarbon to contain about 1.9% thereof, only about 13.5% copper willdissolve into it, as compared with 90% if the iron contains say 0.1%carbon. By increasing the carbon to 2.5% only about copper will dissolveinto it. and, when enough carbon is introduced to form iron cononlyabout copper will dissolve into it.

Applicants further have found, that if the scrap is melted and the ironcontains not more than about 1 to 1.5% carbon, the degree of separationof the ferrous and cuprous materials is lnappreciable from an economicstandpoint. Under such conditions the iron contains so much dissolvedcopper that it will not separate'readily by stratiflcation from theundissolved copper apparently on account of density and surface tensionphenomena involved. Thus, with such low amounts of carbon, not centageof dissolved copper be retained in the iron, but the iron will contain alarge percentage of free copper dispersed through it. resulting in itsbeing impossible to separate a worthwhile amount of copper from the meltor separate therefrom iron which contains only a reasonable amount ofcopper. with more than about 1.5% carbon the recovery of iron and copperrapidly increases, reaching a critical value which makes the processeconomically feasible when the carbon is about 1.75% .and upward,although higher percentages of carbon, up to about 4.3% thereof,ordinarily will be desirable to secure as high a recovery of copper aspossible.

It has also been found that the introduction of carbon into theferrousmaterial decreases both.

its density and its melting point, and for a given temperature makes itmore fluid, and hence by these effects acts to promote stratification ofthe ferrous and undissolved cuprous constituents-of the melt.

It has further'been found that both silicon and manganese, whendissolved into the iron with the carbon. act to promote the overall rateat which stratification occurs, and also act to increase the amount ofundissolved copper recovered. Either or both silicon and manganese usedin this con-, nection cause the iron to be more fluid at any giventemperature and reduce its density, and hence increase the overall rateat which stratiilcation occurs. This increase is very pronounced ascompared to the iron containing only carb'on, particularly asstratification progresses and the amount of copper in the unstratizlledmetal mixture is reduced. In fact the necessary time for completestratification in a commercial sense may in some instances be reducedfrom about 24 hours to about 30 minutes by introducing silicon andmanganese aswell as carbon.

In respect to silicon and manganese acting to increase the recovery ofcopper it has been found that they do-this by degaslfying the melt'priorto stratification. Gases in the melt tend to dissolve in the copper, andtend to be released when the temperature of the melt is lowered or.whenthe pressure on the copper is reduced, such reduction in pressure beingcaused say by tapping metal from the container in which stratificationtakes place. When released the gases tend to rise in the form of bubblesfrom the copper into the iron and carry withthem sufllcient free copperseriously to reduce in many instances the recovery of the free copperfraction of the melt. Preferably, both silicon and manganese are enteredinto the melt, manganese acting to degasify the copper in respect tosulphur dioxide, which is commonly present because of the sulphurcontent of the fuel, and silicon acting to degasify it in respect toother gases.

Preferably the manganese and silicon are entered in the form ofterm-manganese and ferrosilicon so that the manganese and silicon willdissolve into the iron of the scrap rather than into only will a highperthe copper. However, because of the intimate mixture of the ferrousand cuprous materials prior to stratification, the manganese and siliconact to scavenge the copper in the respects mentioned. Sufficientterm-manganese to dissolve about 0.1 to 1% manganese into the iron, andsufficient ferro-silicon to dissolve about 0.5'to 5% silicon into it,may be employed. Preferably enough of these to dissolve into the ironabout 0.5% manganese and about 1.5% silicon is employed. However, if nosulphur is present in the melt, the manganese may be omitted. It will beunderstood in these connections that manganese and silicon, althoughgiving improved results and for that reason preferably employed, neednot necessarily be employed.

Further it has been found, that when enriching the mild steel withcarbon, the zinc content of any brass present may at the same time bereadily removed by practice of the improved method, so that the meltsubjected to stratification will in effect consist substantiallyexclusively of molten cast iron and copper.

The copper fraction of the scrap recovered by the improved processcommonly will contain small amounts of free iron dispersed therein,usually about 2 or 3% thereof. If desired, the copper recovered may thenbe treated for removing the iron impurities, for example may be treatedfor this purpose in a so-called anode, scorlfying, or other suitablefurnace for oxidizing or otherwise burning off the iron impurities, soas to give fire refined copper, and if desiredthe latter may be castinto anodes for further refining.

The carbon enriched iron recovered by the im-- proved process willcontain small amounts of dissolved copper, the exact amount of copperlargely depending upon the amount of carbon entered into the iron asabove explained. Ordinarily, when approximately full advantage is takenof the conditions governing successful operation of the process, thisamount of copper will not exceed about 5% including dissolved copper.Such iron is useful for many industrial applications, and. further, maybe usefully employed as a substitute for iron containing nickel as anaddltion'to steel in forming alloy steel.

Convenient forms of apparatus for practising the improved process aremore or less diagrammaticallyillustrated by theaccompanying drawings, inwhich: v

Fig. 1 is a somewhat schematic vertical section of a standardblast-furnace slightly modified better to adapt it for use in practisingthe improved process;

Fig. 2 is a somewhat schematic vertical section of one form of so-calledholding-furnace for use in practising the improved process;

Fig. 3 is a somewhat schematic verticalsection of a standardcupola-furnace slightly modified better to adapt it for use inpractising the improved process; an

Fig. 4 is a somewhat schematic vertical section of the lower portion ofa standard cupola-furnace with an attachment for better adapting it foruse in practising the improved process.

In practising the invention'with the form of apparatus shown by Fig. lthe procedure followed is in general the same as that of reducing ironores in a blast-furnace. Alternate layers of scrap i and by-product coke3 may be placed in the furnace by entering them successively into thetop of tho furnace from the hopper l by manipulation of the bells 9 andI i the same as is done v in blast-furnace practice. If desired thescrap venient place of disposal.

As shown, the bottom of the furnace is shaped, say by redesigning that,portion of a standard blast-fumace, to form a chamber for collecting avertically elongated pool of the molten metal. Preferably this chamber,because of the preponderant amount of iron in the melt, is madesubstantially conical in shape as indicated at ID. The molten .ferrousand cuprous materials will richment however being largely accomplishedby the carbon monoxide. To promote this action preferably the airentered into the furnace through the tuyeres is preheated to a temperature of about 350 to 800 F. The amounts of air which it is necessary toenter into the furnace will depend upon the size and melting capacity ofthe latter. Ordinarily satisfactory results will be secured by chargingabout 350 to 400 pounds of by-product coke for each 1000 pounds of theiron content of the scrap charged, and, for this amount of coke andiron, forcing about 5000? to 6000 cubic feet (reduced to atmosphericpressur and normal temperature) of preheated air through the tuyres perminute. Under these conditions the gas discharging from the furnace willcontain about 20 0 carbon monoxide.

Preferably, at the start of operations, the fur... nace is charged withcoke to the normal height of the charge and the coke is ignited and thefurnace, such additional coke as may be necessary being added tomaintain the height of the col umn. After the coke is heated toincandescence, and the furnace is thoroughly preheated, the charging ofscrap and additional coke may be commenced.

, By use of a blast-furnace the iron may be read ily enriched with 4 to6% carbon. For insuring degasification of the molten metal for thereasons 20 above explained suflicient ferro-manganese and ferro-siiiconmay be entered with the charge of scrap to insure the necessary amountsof manganese and silicon in the iron.

Preferably a small amount of limestone, say Q.

50 to 100 pounds thereof per ton of iron entered trier, if desired, withthe limestone may b charged a small amount of sodium carbonate, I sayabout 4 pounds thereof per ton of iron, to reduce the amount of sulphurdissolved into the 7 metal.

When the scrap contains brass as, for example, when it consists ofbi-metal clad with gliding metal, the zinc will be driven off in theupper portions of the furnace and escape in the form of fumes throughthe charging ports i5. At the -final temperatures existing, whichpreferably are.

about 2500 to 2800 F., the molten metal, which collects at the bottom ofthe furnace, will contain substantially no zinc, the final fraction ofthe zinc, usually amounting to about 0.2%, going off with the slag.

It will be understood that in operating the furof combustion escapingfrom the top of the fur= nace casing through openings 31. As shown, the

pot is provided with a tap 39 communicating with its bottom portion fortapping oif the cuprous material, and, intermediate its height, with atap H for tapping oil the iron.

.is projected above the plained. In

' stratification.

It will be understood that other forms of boldins-furnaces may .beemployed, for example. the invention on a large scale, the well knowntype of rotary furnace comprising a horizontal, cylindrical, interiorlyrefractory lined drum, into which'an oil and air flame molten metal'tokeep the latter hot, the drum being axially rotatable with; out rotatingthe metal so as to bring a pouring spout below the metal level when itis desired to pour. in which way with such furnace the stratiiled metalsmay be separately poured.

In cases where the surface of the metal in the holding-fumace issubjected to heated gaseous it molten, as the case with the abovedescribed ro-.

products flame for maint would be tary type of furnace, the surface ofthe metal may be covered with a layer of protective flux, say a mixtureof sand and sodium carbonate, for preventing absorption of gases intothe metal to the end of promoting eilective separation of the iron andcopper, as also above described.

Preferably, the metal is maintained at a high temperature in theholding;furnace, say for example 200 to 400 F. above the melting pointof iron, to promote stratification by keeping the iron as fluid aspossible. This temperature also pref erably should not be less than thatmetal is tapped from the furnace, so as to minimize escape from thecopper of any gases -dissolved in it, which gases tend to :be liberatedif the copper is permitted to cool during the progress ofstratification, and, when liberated, tend to carry free copper'into theiron as above exall cases the holding-furnace should be vented to permitescape of such gases as happen to be liberated from the metals.

The metal in the holding-furnace is preferably maintained in' aquiescent condition to promote In cases where the scrap is continuouslymelted it will for this purpose be necessary to eniploy at least twoholding-furnaces, in one of which the metal stands quiescent while theother is being charged. The number of holding-furnaces necessary will ofcourse depend upon rate at which metal is melted in the meltingfurnace.

It has been found that after the molten metal remains quiescent in theholding-furnace from to 30 minutes, depending upon the fluidity of theiron, which fluidity as above explained for a given temperature islargely determined by the carbon content of the iron, the coppercollected will contain only a small amount of iron, and the ironcollected only a small amount of copper,. as above explained. The copperremoved may be cast into pigs, as well as may be the iron,

or the copper may be removed to a refining-furnace for treating it toremove such iron impuri tie as it may contain, as also above explained.

Instead of employing a blast-furnace as-above described, acupola,-furnace, such as is commonly employed for melting cast ironpigs, may be employed for practising the process. However, in such casethe cupola-furnace should be operated to produce the effect of ablast-furnace and, if necessary, the cupola should be modified oraltered to permit such effect to be secured. Ordinarily but about '75pounds of by-product coke are employed ror each 500 pounds of iron to bemelted in a cupola,-furnace, which amount of coke will have noappreciable effect in respect to carburizing the iron. In carrying outthe improved process, however, this amount of coke distance above atwhich the their metal holding capacity relative to the practice,

4 melted in the cupola 61, when 8 with relation to the iron should'bemuch increased,'preferably about to 225 pounds of employed for each 500pounds of iron much above that employed'in standard cupola to insure theformation of the requisite amount of carbon monoxide so as to enrich theBest results are also secured by raising the tuyeres of the standardcupola-furnace' to about twice their usual the hearth to prevent of themelted iron at the bottom of the furnace, and, further, best resultswill be secured by raising the charging port to a considerably greaterdistance above the tuyeres than found in the ordinary cupola, so as tosecure a longer column of coke.

A modified. form of cupola-furnace suitable for practice of theinvention is, shown in Fig. 3. As shown, for the removable bottom of astandard cupola-furnace 43 .a vertically elongated, conical pot 55 issubstituted, the pot being conveniently formed with an outer linedinteriorly with: a refractory layer 49 of firebrick or other refractorymaterial. The cupola may be charged through the charging port 5| withscrap and coke to form alternate layers of scrap 53 and coke 55 to keepthe furnace filled to. Just below the port. Combustion of the coke issupported by the air entered into the lower per-- tion. of the furnacethrough the tuyeres 51. As

the charge is melted it trickles through the col-.-

umn of the incandescent coke and is enriched with carbon by intimatecontact with the ascending carbon monoxide. The molten metal collects inthe pct 45 in which it stratifies to form a mass of molten cuprousmaterial at the bottom of the pot with a superimposed mass of moltenferrous material. The cuprous material may be tapped from the pot fromtime to time through the tap 59 and the ferrous material through the tap81, while slag may be removed through the tap 63 at the upper portion ofthe pot.

As shown in Fig. 4, the cupola,-furnace is .provided with a fore-hearth65 in which the molten metal in the cupola is permitted to stratify.With the apparatus shown by Fig. 4 the scrap it reaches the bottom 69thereof, will flow through the opening or cupola breast Ii through aconduit 13 of refractory material into the iore hearth. As shown, thefore-hearth may be in the form of a cylindrical container of refractorymaterial having its bottom portion formed to provide a verticallyelongated, conical chamber 15'. In this chamber the molten metal willstratify, permitting the cuprous material to be tapped therefrom throughthe tap hole i1 and the ferrous material containing a large amount ofcopper through the tap hole 19, while slag may be removed through thetap hole 8!. A blast will strike strongly through the open breast andkeep the molten metal in the fore-hearth hot. Exit of hot cupola, gasesfrom the fore-hearth is provided by the pipe 83 communicating with thecupola well above the 'tuyeres 85.

The fore-hearth employed may take various forms, for example, may be ofthe well known removable type mounted for rotation on a horizontal axissov that the metal contained therein may be readily poured.

It will be will be operated substantially continuously,

oxidation steel shell ll understood that the cupola-furnace and skilledin the art from the following specific example of the practice of themethod utilizing such a 11 MM"? Assuming there is available a standardcupolathe recovery of its cop.-

be handled in the way v the results any furnace of the type shown inFig. 4, but without a fore-hearth, the cupola having an internal dimeterof 42 inches, the water jacketed tuyres of this furnace, positioned 16inches above the bottom or hearth 89 of Fig. 4, may be raised to about33 inches above it to insure agalnstthe blast entered through the tuyresoxidizing the from of the molten metal collecting at the bottom of thefurnace. The charging door, which in such a standard furnace is about14.5 feet above the tuyres, preferably should be raised to position itabout 20 feet above them to provide a longer column of cok. In operatingthis cupola it preferably should be first'filled with .a column ofby-product coke and the coke burned for one hour with a blast of about2500 to 3000 cubic feet (reduced to atmospheric pressure and normaltemperature) of air per minute entered through the tuyres to bring thecolumn of coke to incandescence and preheat the furnace prior tocharging scrap, the air being preferably preheated, say from 350 to 650F. Such coke as is necessary to maintain a column of requisite heightmay be entered during this period. When the scrap employed consists ofsheet mild steel about 0.05 of an inch thick coated with a layer ofgliding metal about 0.01 of an inch thick, alternate layers of thisscrap entered into the furnace at such rate as to melt about 3 to 3 tonsof scrap per hour. For each 500 pounds-of scrap entered 175 to 200pounds of by-product coke should be entered, preferably with aboutpounds of limestone, '1 pound of sodium carbonate, and sufficientterm-manganese and ferro-silicon to insure the presence of about 0.5%man'ganese and about 1.5% silicon in the melt. After the scrap isentered the air blast and coke may be may be increased to about 5500 toabout 6000 cubic feet per minute. The molten metal may be tapped fromtime to time through the breast H of Fig. 4, which under theseconditions is normally plugged, into a rotary holding-furnace of thetype hereinbefore tion as may occur in the cupola being ignored. Priorto entering the melt into the holding-furnace the lattermay be preheatedto about the temperature of the melt, namely, to about 2500 to 2800 F.Upon the surface .of the molten metal in the holding-furnace may bemaintained a heavy layer of molten sodium carbonate for protecting themolten metal from the combustion gases in the furnace. Two suchholding-furnaces may be employed, each of sufficient capacity to permitthe molten metal charged thereinto to remain quiescent for about 30minutes to enable the molten iron and copper to stratify. Pigs cast ofthe iron tapped from the holding-furnace will contain about 3 carbon andabout 6% copper. Pigs cast of the copper tapped from theholdingfurnace'will contain about 3% iron.

described, such stratifica-.

blowing the column with 19 It will also be understood, that although itis preferred to melt the scrap in the presence of combustiblecarbonaceous material and carbon I melting-f 10%, other may be employedand the carbon entered into the iron in other own ways of carbulriaingiron. in such ces, however, not be as satisfactory as th secured in thepreferred way of practising the method. Still iiurthenit will be understood that partial stratihcation of the melt need not be eiiected priorto charging the molten. metal into the holding-fa. as, for example, themolten metal may be tapped substantially coo tinuo from the melting-decowithout maintaining a pool of metal in that face or in a fore-hearth inwhich stratification can occur.

or all the and such without departing from the spirit of the invention.

We claim: I 1. The method of separately recovering cuprous .and ferrousconstituents of scrap consisting of low carbon steel and associatedcopper or brass which comprises melting the scrap. enriching the moltenferrous constituent with -carbon, silicon and manganese to cause it tocontain at least about 2% carbon, at least about 1.5% silicon, and atleast about 0.3% manganese, and separatingferrous and cuprousconstituents of the scrap so treated by permitting them to stratifywhile in the molten condition at temperatures above the melting point ofthe carbon enriched ferrous constituent.

2. The method of separately recovering cuprous and ferrous constituentsof scrap bi-metal consisting of mild steel coated with a welded on layerof gliding metal which comprises charging a vertical stack-like furnacewith coke to form an elongated coke column; burning the coke while anascending blast of air thoroughly to ignite the column and heat thefurnace to a temperature above the melting point of the scrap; chargingscrap, coke, ferro-manganese and ferro-silicon to the heated furnacewhile continuing the blast whereby to melt the scrap, distill off thezinc of the brass, and enrich the molten ferrous constituent of thescrap with at least about 1.75% carbon and dissolve at least about 0.5%silicon and at least about 0.1% manganese into it, the amount of cokeand scrap charged being sufficient to maintain the column; the blast'andthe amount of coke in proportion to the ferrous constituent of the scrapbeing such as to' produce sumcient carbon monoxide to effect suchenrichment of said ferrous constituent with carbon; from beneath thecolumn holding into a container and it quiescent in the latter attemperatures above the melting point of the carbon enrichedandwithdrawing molten scrap so treated I said constituent to contain atleast 1.75% carbon,

at least 0.5% silicon, and at least 0.1% manganese,

ferrous and cuprous constituents d. The method of separately recoveringcuprous and ferrous constituents of scrap consisting of low carbon steeland associated copper or brass which comprises melting the scrap,incorporating into the molten sumcient carbon stituent to contain atleast 1.75% carbon and at least 0.5% silicon, and separating ferrous andcuprous constituents of the scrap so treated by permitting them tostratify while in the molten condition at a temperature above themelting point of the ferrous constituent containing said carbon andsilicon.

5. The method of separately recovering cuprous and ferrous constituentsof scrap consisting of low carbon steel and associated copper or brass,which comprises passing the scrap in molten condition downwardly throughan elongated column comprising ignited coke; decreasing the density andsolubility for copper of the molten ferrous constituent byblowing thecolumnwith an ascending blast of air f or burning the coke and producingcarbon monoxide, the latter treating the scrap as it descends throughsaid column for enriching its ferrous constituent with carbon to bringits carbon content up to at least about 1.75% for securing said decreasein density and solubility for copper; also feeding to the upper portionof said column suilicient ferro-silicon to dissolve an appreciableamount of silicon, not less than. about 0.5%, into the ferrousconstituent of the scrap; and separating ferrous and cuprousconstituents of scrap so treated by permitting them to stratify while inthe molten condition at temperatures above the melting point of thecarbon enriched, silicon cont'aining, ferrous constituent.

6. The method of separately recovering cuprous and ferrous constituentsof scrap consisting of low carbon steel and associated copper or brasswhich comprises charging the scrap and coke into I a stack-like furnaceabove an elongated column therein comprising ignited coke, the amount ofcoke and scrap charged being sufflcient to maintain said column as thecoke burns and the molten scrap is removed from beneath the stack,blowing said column with a vertically ascending blast of air to burn thecoke and produce carbon monoxide, whereby to melt the scrap and to treatwith carbon monoxide the molten scrap as it descends through said columnfor enriching the molten. ferrous constituent of the scrap withsuflloient carbon to bring its carbon content up to at least about1.75%, also charging into said furnace above said column sufficientferro-silicon to dissolve an appreciable amount of silicon, not

ferrous constituent of the scrap and silicon to cause said con I 0.1%respectively, into i2 less than about 0.5%, into the ferrous constituentof the" scrap, withdrawing treated molten "scrap from the bottom portionof said stack and separating ferrous and cuprous constituents of thescrap by permitting them to stratify while in the molten condition attemperatures above the melting point of the carbon enriched,silicon-containing, ferrous constituent.

'7. The method of separately recovering cuprous and ferrous constituentsof scrap consisting of low carbon steel and associated copper or brass,

which comprises passing the scrap in molten condition downwardly throughan elongated column comprising ignited coke; decreasing the density andsolubility for copper of the molten ferrous constituent by blowing thecolumn with an ascending blast of air for burning the coke and producingcarbon monoxide, the latter treating the scrap as it descends throughsaid column forenriching its ferrous constituent with carbon to bringits carbon content up to at least about 1.75% for securing said decreasein density and solubility for copper; also feeding to the upper portionof said column sufficient ferro-silicon and ferromanganese to dissolveappreciable amounts of silicon and manganese, not less than 0.5% and theferrous constituent of the scrap; and separating ferrous and cuprousconstituents of scrap so treated by permitting them to stratify while inthe molten condition at temperatures above the melting point of thecarbon enriched, siliconand manganese-containing, ferrous constituent.

8. lhe method of separately recovering cuprous and ferrous constituentsof scrap consisting of low carbon steel and associated copper or brasswhich comprises charging the-scrap and coke into a stack-like furnaceabove an elongated column therein comprising ignited coke, the amount ofscrap is removed from beneath the stack, blowing said column with avertically ascending blast of air to burn the coke and produce carbonmonoxide, whereby to melt the scrap and to treat with carbon monoxidethe molten scrap as it descends through said column for enriching themolten ferrous constituent of the scrap with sufficient carbon to bringits carbon content up to at least about 1.75%, also charging into saidfurnace above said column suillcie t ferro-silicon and farm-manganese todissolve appreciable amounts of silicon and manganese, not less than0.5% and 0.1% respectively, into the ferrous constituent of the scrap,withdrawing treated molten scrap from the bottom portion of said stackand separating ferrous and cuprous constituents of the scrap bypermitting them to stratify while in the molten condition attemperatures above the melting point of the carbon enriched, siliconandmanganesecontaining, ferrous constituent.

RICHARD A. WILKINS.

EDWARD S. BUN'N.

